Belt Squeals When AC Is On – Reasons and Fixing Process

Just like vehicles are built with an expected lifespan, the components that make up the entire vehicle have their individual estimated lifespan. However, some parts get damaged faster before attaining their targeted time frame.

For instance, if a belt squeals when AC is on in your car, that’s a symptom of a faulty component right there. Therefore, it is crucial to find out the cause of the occurrence and fix it as soon as possible.

Meanwhile, this article unveils the causes of belt squeals when AC is on and how to rectify the issue. So why not take a moment to digest such valuable information below?

belt squeals when ac is on

Causes of Belt Squeals When AC Is On

A squealing belt can emit a loud, frustrating noise if you fail to rectify the issue immediately. However, it is vital to know the cause of the problem before trying to figure out a solution.

So, if your AC belt squeals when you turn on your car’s air conditioning system, the following may be the cause like worn and loose serpentine belt or bad ac compressor.

A loose or worn serpentine belt

The serpentine belt is designed to power a vehicle’s alternator, power steering pump, water pump (in some cars), and the air conditioner’s compressor. The component kicks in and transmits rotational energy to these components when a car is running.

The belt is also called a drive belt because it drives multiple peripheral parts in an automobile’s engine. Usually, when you turn on your car’s air conditioning system, the AC compressor is automatically engaged.

Once this occurs, the load is placed on the serpentine belt and the car’s engine. Over time, the grooves on the serpentine belt that enables it to engage the pulley’s grooves wear out gradually due to friction.

After a while, the drive belt becomes worn out and unable to fit into the grooves on the pulley as expected. This loose fit will eventually result in a loud squealing noise as the AC continues to work. If you hear noise when AC is on in a car or blows smoke, kindly check it out and fix it ASAP.

A cracked or broken drive belt

The experience is somewhat similar to the one above. A broken serpentine or drive belt will produce a loud squeaking, squealing, or slapping noise when you turn on the AC in your car.

Unfortunately, the problem doesn’t end with the air conditioner. A cracked serpentine belt will affect the proper functioning of a car’s alternator, water pump, and power steering pump.

In other words, a broken serpentine belt will result in a squealing noise, and lead to heavy steering, improper coolant circulation and engine overheating, etc.

Other Reasons for Squealing Noise of Car AC

Besides a worn-out or broken serpentine belt, some other issues may be responsible if your car’s drive belt squeals when AC is turned on. Some of the other issues include the following.

Faulty AC compressor clutch

The compressor clutch is responsible for engaging the compressor and pressurizing the entire air conditioning system to trigger the process that releases cold air. Unfortunately, this component can fail due to a bad clutch coil, a blown fuse, or poor ground.

When this happens, the AC will automatically release a loud squealing noise. Therefore, if you constantly hear this noise when you turn on your AC, verify whether you have a bad AC compressor.

Defective AC compressor pulley and bearing

The AC compressor pulley is the part of the air conditioning system that is connected to the serpentine belt. The component rotates as the serpentine belt transmits rotational energy when the engine runs.

The compressor pulley also features a bearing, which enhances its rotation. However, if these components become damaged over time, you will eventually hear a loud squealing noise when AC is turned on.

How Do You Fix A Squeaky AC Belt?

Fixing a squeaky AC belt is pretty straightforward. Simply get a bottle of WD-40 and spray some of the content on the drive belt until you can’t hear the noise anymore. You can do this while the car’s engine is running to know when the noise ceases.

Also, you can use a bar soap if you don’t have a bottle of WD-40 handy at the moment. Simply rub the bar soap on the AC belt a couple of times. Please turn on the car to verify whether it stops the unpleasant squeaking noise.

Track and fix the leading cause of the problem if the soapy water did not fix it.  For example, if a loose or worn belt is the culprit, adjust or replace the belt with ACDelco ac belt to resolve the issue. If that is not the culprit, examine the compressor clutch and pulley. If the clutch is wobbling or the pulley teeth are bent or damaged, replace it.

Can I Put WD 40 On A Squeaky Belt?

WD-40 can silence the noise if your car squeaks when AC is on. However, in some cases, the fluid might weaken and break down your car’s serpentine belt. This is because WD-40 is a petroleum-based product.

 Therefore, you may want to apply any other method to stop the squeaky noise coming from your worn-out serpentine belt. For example, you can spray soapy water on the belt or use your common deodorant to stop the noise if your drive belt squeal when AC is on.

noise when ac is on in car

How Much Does It Cost To Fix A Squeaky Belt?

Fixing a squeaky belt costs around $100 – $195. The total cost comprises of $25 – $75 for parts and $75 – $120 for labor fees, respectively.

If your AC is making a screeching sound due to a bad serpentine belt, you can simply get the part from an auto parts shop across the street and fix it yourself in your garage (if you’re a DIYer).

 Of course, this will save you a whopping $75 – $120 labor cost. However, kindly contact an expert auto technician if you can’t handle it.


There’s no need to worry if your belt squeals when AC is on. It’s just a sign of a worn, loose, or broken serpentine belt. All you need to do is get any of the substances recommended above in this article to stop the noise.

However, if your AC compressor squeals on startup due to an excessively damaged AC belt, this might be the right time to replace the belt. Again, the parts and labor fee will only cost you a few bucks.

Solomon Osuagwu

Osuagwu Solomon is a vetted auto mechanic with over ten years of experience in the garage and five years of experience as a service writer. He prides himself in writing accurate information on professional repair guides, DIY repair guides, buyer’s guides, comparisons, and car reviews. If he’s not in his repair garage, he’s writing automotive blogs to help car owners and fellow mechanics to troubleshoot and proffer solutions to several car problems.

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